The asymmetry of the individual phases is also monitored in three-phase electric motors in particular because it allows conclusions on the condition of the motor or its load behavior.
For this purpose, all three phases have been monitored heretofore and a characteristic value was determined from the individually measured phases. If the characteristic value was outside a specific range, the motor was immediately deactivated.
Such a method has been known from e.g. EP 2 083 493, where a maximum current was first defined by means of the three determined phases, and three asymmetry values were subsequently determined which were jointly incorporated into a motor model.
Such a method is complex from several points of view. On the one hand, all three phases have to be measured, and on the other hand, a large number of calculations is required.
It is therefore the object of the invention to provide a method and a device for the detection of current asymmetries in three-phase circuits, which solves one or several disadvantages of the prior art in an innovative manner.